Electron tubes and magnetrons have been used extensively in radar, navigation, electronic countermeasure, and microwave devices. Thermionic emission cathode is one of the key components of electron tubes and magnetrons and plays an important role in the operation of these devices. Up to now, thoriated cathode (ThO2—W) which is still widely used in electron tube and microwave oven magnetrons. Nevertheless, it is necessary to find other environment-friendly elements to substitute thorium as thorium is a radioactive element. Lanthanum oxide-molybdenum (La2O3—Mo) cathode was found to have a certain thermionic emission property. However, during the operation of magnetrons at an external magnetic field, a large number of electrons emitted back-bombarded the La2O3—Mo cathode, resulting in the evaporation and loss of lanthanum on the cathode surface and thus the poor emission stability of this kind of cathode. Among all the rare earth elements, lutetium (Lu) has the highest melting point. In this patent, we propose a kind of Lu2O3 doped Mo cathode for thermionic emission and its fabrication methods.